Process of preparing tungsten titanium carbide



UNITED STATES PATENT OFFICE PROCESS OF PREPARING TUNGSTEN TITANIUMCARBIDE No Drawing. Application December 13, 1937,

Serial No. 179,552

6 Claims.

This invention relates to a process of forming a carbide of tungsten andtitanium, and more particularly to a process for forming a carbidecorresponding substantially to the chemical formula WTiCz.

The principal object of the invention is the production of a carbidecontaining tungsten and titanium which will be extremely hard and ofgreat value and utility as a material for use, in accordance with theusual principles of; powder metallurgy, in the production of hardcompositions of matter, in order to effect therein great hardnesscombined with great strength, together with a low thermal conductivity,and other characteristics, which will enable the hard compositions ofmatter made from such carbide material to have great utility anddurability when used as the cutting points in the cutting of metal athigh speeds, when used as dies, and when used to providecorrosion-resisting surfaces, and for other similar uses.

A further object of the invention is the production of such a carbide,containing tungsten, which, when used in the production of hardcompositions of matter, in accordance with the usual principles ofpowder metallurgy, and with a binder material containing powderedtungsten or molybdenum, or carburized tungsten or molybdenum, or othercompounds of tungsten or molybdenum, with or without nickel or cobalt,will yield none of its carbon content to any of the metals so used as abinder in such hard compositions of matter.

A still further object of the invention is the production of such acarbide which, when used as an ingredient in such a hard composition ofmatter, renders it possible to include in such hard composition ofmatter a higher percentage of metallic tungsten as a binder than hasbeen practicable heretofore, whereby the toughness and breaking strengthof such composition of matter can be increased without a materialdecrease of the hardness and cutting ability of such composition ofmatter.

Further objects of the invention, together with details of the steps bywhich the invention is put into practice, will be apparent from thefollowing specification.

The new carbide substance which I have invented, and obtained by theprocess herein described, is apparently a double carbide of tungstem andtitanium corresponding to the chemical formula WTiCz, and containingsubstantially 71.9% W, 18.7% Ti, and 9.4% C, and it has been invariablyobtained by following the process herein described, regardless of widevariations in the amount and proportions of the tungsten and titaniumcontent, the excess of tungsten or titanium remaining uncombined, so asto be readily separable therefrom, along with the other resultingsubstances.

The new carbide substance is prepared by heating, tungsten, or asubstance containing tungsten such as tungsten oxide, or alloys oftungsten, with titanium, .or a substance containing titanium, such astitanium'oxide, in'the presence of carbon, in a menstruurnmetal, forwhich purpose nickel has been found to be preferable, the substancebeing then separated by chemical and mechanical means from the resultingmass. I have, likewise, prepared such carbide'substance repeatedly byemploying as a menstruum metal cobalt, or a mixture of nickel andcobalt, andit is possible that menstruum metals other than nickel andcobalt may be used. However, because of the low cost and the ease of itsremoval, I c0nsider the use of nickel to be preferable from a commercialstandpoint. The amount of menstruum metal or metals, may vary widely,from an efiective amount up to an amount considerably in excess of thetung stencontent, and I have found that the use of nickel or cobalt inan amount approximately equal to the amount of tungsten gives the bestresults from a commercial standpoint. If only a small amount ofmenstruum metal is used, it must function by solution of a little of thetungsten andtitanium at a time, such dissolved metals apparentlycombining in solution to form the carbide, thus freeing the menstruummetal'so that it is available to dissolve a further quantity of thetungsten and titanium. As will be apparent, the time necessary tocomplete the reaction under such circumstances is unduly prolonged.

As stated above, thepresent application iS'di", rected to the process bywhich this new carbide substance is formed, and the new carbidesubstance, that is, the, product so "produced, is described and claimedin my co-pending application, Serial No. 179,551, filed of even dateherewith, to which reference is hereby made.

I have likewise invented certain new and'useful improvements in hard,compositions of mat-, ter containing this new carbide substance asaningredient, described and claimed in my copending application, SerialNo. 179,553, filed of even date herewith, and in a processior makingsuch hard compositions of matter, described and claimed in mycopending'application, Serial No. v

Search that F-ul UliLlUflPUl and graphite chips, all placed together ina graphite crucible. I have also incorporated the tungsten in the formof W03 in such melts, with equally good results.

I have found it advisable to mixwith the other materials chips orturnings of graphite, in an amount constituting about 5% of the tungstenand titanium materials combined. The mass resulting from the heatingprocess, after cooling, is

crushed, treated with water solutions of hydrochloric acid and a smallamount of nitric acid, at boiling temperatures, or with similaroxidizing acid solutions such as hydrochloric acid to which potassiumperchlorate has been added, treated with ammonia or other hydroxidesolutions to remove W03, again treated with aqua regia, or otheroxidizing acid solutions, to dissolve the .Ni, and again treated withhydroxidesolutions to dissolve any remaining W03. At various'stages,during such treatments, the powdered material is subjected to mechanicalconcentration, as by panning or gravity concentration, as on a Wilfleytable, to remove loose graphite and particles of light impurities. Theparticles remaining after such chemical separation of other compounds,are grey particles having a metallic lustre. These particles are furthertreated, preferably in platinum dishes, with strong solutions ofhydrofluoric acid, at a temperature up to its boiling point, to dissolvesuboxides or blue oxides of tungsten, such as W02, and any otherimpurities. The hydrofluoric acid solution is removed by'repeatedwashing and decantation, and the remaining particles are carefullypanned or otherwise concentrated, as by gravity methods, and dried, theremaining particles being grey in color, with high metallic lustre,having surfaces which are predominantlyconchoidal, and of a sizeaveraging greater than .01mm. in' largest cross-section dimensions.

As a specific example of the process followed in the formation of suchnew carbide substance, and the characteristics, as shown by test, of theproduct obtained thereby, the following procedure was followed in oneinstance:

There was placed in a crucible, 6 in diameter of substantially puregraphite:

Grams Tungsten rods 1840 Powdered T102 800 Ni melting stock 2800 Thegraphite crucible, with such contents therein, was placed in an electricinduction furnace and heated, during a period of approximately an hour,to a temperature of 2100 C., and maintained at such temperature for a'period of eight hours. After cooling, the product of such heatingprocess was removed by breaking away the graphite crucible, and the masswas crushed by hammerand by a jaw crusher, together with coarse ballmilling, until the particlesthereof would pass a 40-mesh screen. Theparticleswere repeatedly treated with water mixtures of hydrochloricacid to which a small amount of nitric acid had been added, the acidmixture being repeatedly boiled. After such acid treatments, theparticles were treated with ammonia solutions, to remove any W03, andwere again treated with aqua regia to dissolve nickel and nickel alloysand other impurities, and finally were again treated with ammoniasolutions. At various stages during such acid and hydroxide treatments,the particles were subjected to mechanical concentra tion by panning andwere also concentrated by gravity methods on a Wilfley table to remove lloose graphite and other light impurities, leavcles were obtained.

A carbon analysis wasmade of samples from such particles, and showed acarbon content of 9.40% C, which is quite close to thecarbon ,con-

tentof 9.39% C which theoretically should be present according to theformula WTiCz. This discrepancy of the carbon content found is withinthe error of analysis of the carbon content of materials of this type. Atest of the tungsten and were found to have a specific gravity of 9.72,

which is much lower than would be indicated theoretically for a mixtureof WC and TiC in the proportions of the metallic contents found bytests. Inasmuch as the specific gravity of WC is 15.64 and that of T10is 5.0055, the calculated specific gravity, on the assumption that thisproduct is amixture of WC and T10, would be 10.29., The melting point ofthe product was found to be higher than that of WC (2867:50" C.) and maybe higher than that of TiC (3146:50 ,C.). If the substance were a solidsolution of TiC in WC, that is, a eutectic, one would expect the meltingpoint to be lower than that of WC. Particles of the new carbide,substance were treated with a standardizedsolution of hydrofiuoric acidcontaining one drop of nitric acid and were found to dissolve in twohours, Whereas an equivalent amount of a mixture of WC and T10 wasdissolved in the same solution in less. than twominutes.

In order to test further the new carbide substance W'IiCz, as comparedwith a mixture of WC and TiC having the same ultimate metallic content,pairs of test pieces of hard compositions of matter were formed, asdescribed in my copending application, Serial No. 179,554, and using thesame amount of the same binding materials, and following exactly thesame process, except that one contained WTiCz and the other contained anequivalent amount of a mixture of WC and T10. A number of such pairs oftest pieces were made, using different binding materials, and withdifferent proportions of carbide material and of binding material. Inevery case thehard compositions containing the new carbide substanceW'IiC2 were found to exhibit a characteristically lower thermalconductivity-thanthose made with mixtures of WC andTiC', showedgreater-strength and hardness, and likewise showed on repeated tests, inwhich such new hard compositions of matter were used as a metal-cuttingtool point in machining steels and copper-silicon cast iron, muchgreater resistance to cratering and resistance to erosion and wear fromchips of both steel and cast iron, the compositions containing WTiCzlasting from four to five times as long as did' the compositionscontaining mixtures of WC and TiC, when used under identical conditionsin the same machine, and cutting the same material at the same rate ofspeed.

The new carbide substance has been manufactured on a commercial basis inlarge quantities, and has been unvarying in its physical characteristicsand in its chemical analysis, being always produced in the expectedquantity, as particles of a rather uniform size, with high metalliclustre, and with the surfaces of the particles predominantly conchoidalas seen under a high-power microscope.

I believe that the hard carbide substance, made by the processdescribed, is a new chemical compound corresponding chemically to theformula WTiCz. My reasons for such belief are (1) the unvaryingcomposition of the substance produced as described and alwayscorresponding to the formula WTiCz by analysis, even when the quantitiesof the ingredients; of the mixture initially heated are widely varied toinclude a large excess of W or of Ti; (2) its chemically differentbehavior when treated with aqua regia, as compared with WC and TiC, aswell as its chemically different behavior when treated with hydrofiuoricacid containing a small amount of nitric acid; (3) its producing, whenformed into a hard composition of matter in a binder of nickel or cobaltor other binder material, a composition which lasts from four to fivetimes as long as a similar hard composition of matter made inidentically the same way but with a mixture of WC and TiC, and havingthe same ultimate chemical analysis; (4) the characteristically lowerthermal conductivity of hard compositions of matter containing it; (5)its lower density, as compared with that of a mixture of WC and TiChaving the same ultimate analysis; (6) its melting point, which ishigher than that of WC or a eutectic.

As stated above, the process herein described invariably produces acarbide material containing the same proportions, in spite of repeatedefforts to form other tungsten titanium carbides by incorporating in themixture an excess of tungsten or titanium. While nickel is preferablyused as the menstruum metal, it will be understood that changes may bemade in the menstruum metal used, in the amount of menstruum well as inthe means used for effecting mechani-' cal separation of impurities,without departing from the spirit of the invention which is defined inthe following claims:

What I claim is:

l. The process of producing a compound containing tungsten and titaniumin monatomic ratio combined with one atom of carbon for each atom ofmetal, which comprises reacting such metals with carbon in a moltenmetallic menstruum selected from the group consisting of nickel andcobalt.

2. The process of producing a new chemical compound corresponding to theformula WTiC2, which comprises reacting tungsten and titanium withcarbon in a molten menstruum of one or more metals selected from thegroup consisting of nickel and cobalt, and separating the compound fromthe resultant mass.

3. The process of producing a new chemical compound corresponding to theformula W'IiC2, which comprises heating tungsten and titanium in thepresence of carbon and in a molten metallic menstruum selected from thegroup consisting of nickel and cobalt at a temperature above 1600 C.,and separating said compound from the resultant mass.

4. The process of producing a carbide containing tungsten and titaniumin monatomic ratio, which comprises heating tungsten and titanium in thepresence of carbon in a molten metallic menstruum selected from thegroup consisting of nickel and cobalt at a temperature above 1600 C.,and treating the resultant mass with an oxidizing acid solution and witha hydroxide solution, separately, to separate the remainder of the massfrom said carbide.

5. The process of producing a carbide containing tungsten and titaniumin monatomic ratio, which comprises heating tungsten and titanium in thepresence of carbon in a menstruum of molten nickel, and separating saidcarbide from the resulting mass.

6. The process of producing a carbide containing tungsten and titaniumin monatomic ratio, which comprises heating tungsten and titanium in thepresence of carbon in a menstruum of molten nickel at a temperature ofapproximately 2100 0., and separating said carbide from the resultingmass.

PHILIP M. McKENNA.

